Water purification methods

ABSTRACT

Treating water with various grades of attapulgite clay and sepiolite using contacting or percolation techniques removes substances not removable by standard water purification methods under many conditions. Substances such as pesticides, toxins, hormones, heavy metal cations and viruses are removed from water by adsorption upon the clay surface. When contacting is employed, the clay containing the adsorbed substances is subsequently removed by sedimentation or filtration. The clays can be regenerated by appropriate chemical or thermal techniques.

This is a division, of application Ser. No. 636,263, filed Nov. 28,1975, now U.S. Pat. No. 4,054,515.

BACKGROUND OF THE INVENTION

The shortage of pure drinking water is rapidly becoming a seriousproblem. Currently available methods for purifying water from naturaland reclaimed sources are generally incapable of removing certainchemicals and biologically active substances that are appearing in watersupplies in alarmingly increasing proportions. It appears thatbiologically active substances that are intentionally or accidentallydumped into our ponds, streams and rivers or enter ground strata viaseptic systems could become potentially dangerous substances when thewater from these sources is treated by conventional means and iseventually used for drinking.

Standard methods for purifying water such as coagulation, sedimentation,filtration and chemical treatment are effective for removing mostcontaminants and for killing most of the microorganisms present. Thesemethods, however, are not completely effective for removing substancessuch as hormones, pesticides, viruses, toxins and heavy metal cations.The use of female steroids for birth control purposes, for example, andgrowth hormones for fattening-up beef and poultry, has resulted insignificant quantities of these hormones finding their way intomunicipal water supplies, particularly in large metropolitan areas.

Methods for the treatment of sewage, such as removal of solids byflocculation followed by sedimentation and centrifuging, and removal ofbacteria by chemical treatment are generally ineffective for removinghormones and viruses. When the "harmless" liquid effluents from sewagetreatment plants are dumped into inland waters these hormones are stillpresent in the water. When inland waters are subsequently used asbackups for water reservoirs and other storage facilities for municipalwater supplies, these intractable contaminants end up in water that isused for drinking purposes. Subsequent purification procedures aregenerally incapable of removing these hormones so that it is possiblefor them to enter the human body along with the drinking water. The sameproblem, in more or less increasing proportions, is true for othersubstances such as viruses, toxins, heavy metal cations and pesticideresidues.

Another potential source contributing to the human self-contaminationcycle is the backyard swimming pool. Viruses, toxins and hormones whichare deposited in these backyard pools gradually increase inconcentration since they are generally immune to the effects of routinefiltering and chemical treatment. When the pools are eventually emptiedthese biologically active substances could conceivably reach thebathroom and kitchen water taps. This is particularly true for largeinland municipalities where the effluents from sewerage treatment plantscannot be discharged directly into the sea from which the possibility ofreturn is extremely remote.

The purpose of this invention, therefore, is to provide methods andmaterials for removing potentially harmful substances which aregenerally immune to standard sewage treatment and water purificationprocesses from waste streams and/or potable water.

SUMMARY OF THE INVENTION

Treating water with certain minerals removes substances which do notrespond to other methods of water purification. One embodiment comprisesthe use of attapulgite clay powder in combination with alum for treatingpotable water. A further embodiment comprises the method of percolatingwater through a column containing granular attapulgite clay subsequentto standard purification treatments or prior thereto.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side sectional view of a percolation chamber according tothis invention;

FIG. 2 is a front perspective view of an alternate embodiment of thedevice of FIG. 1; and

FIG. 3 is a cross-sectional view of the embodiment of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In order to determine the adsorptivity of clay materials for varioustype viruses the following series of tests were performed.

Since the adsorption properties of clay are a known function of theavailable surface and surface characteristics of the clay resulting fromthe thermal treatment of the clay and the particle size, the clay wasclassified according to fineness of grind and thermal treatment. Inorder to determine virus adsorption over a wide range of sizes, arelatively small virus and a relatively large size virus were employed.Attapulgite clay products, consisting of magnesium aluminum silicate,and commercially available from the Floridin Co., Berkeley Springs, W.Va., were used as typical examples of commercially available andfeasible products for the purpose of this invention. The attapulgiteclay having an average particle size of approximately 26μ was used as afine grade clay for comparison to a clay having a mean particle size ofapproximately 45μ as a coarse grade clay.

Certain high-sorbency, high-surface-area clay minerals--namely,attapulgite, sepiolite, and other minerals similar to attapulgite thatare classified roughly as palygorskites, that are commercially availableat economical prices and where large worldwide reserves exist--wereconsidered to be of prime interest for evaluation in this invention.With these minerals the adsorption of ions, larger molecules andmaterials of colloidal size occurs on the outer surfaces of the needlestructure and surfaces resulting from cleavage where availability ofthese surfaces is limited in access by the pore sizes of largerparticles resulting from needle agglomeration. Consequently, theadsorptivity they exhibit is strongly dependent on their processing.

Clays used in this study and their processing are described below:

HVM -- high volatile matter. This type has been dried at lowtemperatures, has the highest BET (Brunauer, Emmett, Teller) surfacearea and surface available for adsorption and is capable of slaking inwater. Thus, in water systems this grade can only be used in contactingstudies.

RVM -- regular volatile matter. RVM clays have been semi-calcined athigher temperatures (approximately 500° F.) than HVM clays. They exhibitabout half the BET surface area of the HVM clays, but only slightly lessavailable surface. They still are slakeable to some extent but notentirely. Therefore, RVM products can only be used in contactingstudies. Because a certain percentage of the clay is nonslaking,porosity of agglomerates becomes of importance with this grade and hasan effect on adsorption of colloidal particles--small pores will notadmit large particles and thus available surface is decreased.

LVM -- low valatile matter. LVM clays are calcined at highertemperatures (approximately 1000° F.) which result in particlesintering. Particles do not slake in water and this grade is the onlyone of the three suitable for percolation studies in aqueous systems.Because of sintering (and possibly structure collapse) LVM clays exhibitthe lowest available surface and a much smaller pore size distributionand total pore volume than the RVM clays. The reduced availability ofpore surface is reflected in very poor adsorption of colloidal particlesparticularly in granular grades. Grinding LVM granulars into finepowders increases the available surface to a major extent. Consequently,when considering adsorptive surface available for molecular contaminantsin water HVM>RVM>LVM. For molecular agglomerates and colloidsHVM>RVM>>>LVM and powdered LVM>>granular LVM.

The clays and minerals used in the following examples are descibed belowin tabular form.

For the materials listed, the free moisture (FM) was determined bydrying the material to a constant weight at 220° F. and the dry particlesize was determined by using an Alpine classifier. The attapulgiteproducts are commercial products available from the Floridin Co., asdescribed earlier. The sepiolite material, designated X-1000, is acommercially available clay product from the Industrial Mineral VenturesCo., Golden, Colo. The amorphous zeolite is a fine particle sizesynthesized sodium aluminum silicate available from the J. M. HuberCorp., Havre de Graze, Md.

    ______________________________________                                                                          Dry Particle                                                         %        Size                                                                 Free     %                                           Designation Compositon   Moisture +44u                                        ______________________________________                                        Fine Ground HVM                                                                           Colloidal                                                                     Attapulgite  14.2     1.4                                         Coarse Ground                                                                             Colloidal                                                         HVM         Attapulgite  15.0     84.2                                        Fine Ground RVM                                                                           Semi-calcined                                                                 Attapulgite  5.0      1.1                                         Coarse Ground                                                                             Semi-calcined                                                     RVM         Attapulgite  7.5      13.2                                        Fine Ground LVM                                                                           Calcined                                                                      Attapulgite  0.5      0.18                                        Coarse Ground                                                                             Calcined                                                          LVM         Attapulgite  0.2      1.8                                         30/60 LVM   Granulated,                                                                   Calcined                                                                      Attapulgite  0.1      95% through                                                                   a 30 mesh                                                                     screen and                                                                    on a 60 mesh                                                                  screen                                      Sepiolite   Colloidal                                                         X-1000      Sepiolite    12.2     0.15                                        Amorphous   Sodium                                                            Zeolite     Aluminum                                                                      Silicate     6.0        --                                                    (an amorphous                                                                 zeolite)                                                          ______________________________________                                    

In these studies contacting consists of adding powdered clay tocontaminated water, stirring for a specified period of time at aspecified temperature and filtering to remove the clay plus adsorbedmaterial. This technique can be practiced using powdered HVM, RVM andLVM grades. Percolation consists of passing the contaminated waterthrough a column packed with granular LVM grades at a prescribedthroughput rate until the sorptive capacity of the column is exhausted.The capacity of the column is inversely proportional to the ratesused--higher rates result in lower capacities. In distinction frommechanical filtration the capacity is much lower for largercontaminating particles (colloids and molecular agglomerates) than it isfor molecular contaminants.

Two types of viruses were used in this study to exemplify the range ofpossibilities available in clay surface-virus adsorption interactions inaqueous media. Polio virus, Type I, is a small (˜20 mμ) virus with a RNA(ribonucleic acid) core; Herpes simplex is a larger (˜200 mμ) virus witha DNA (deoxyribonucleic acid) core.

                  EXAMPLE 1                                                       ______________________________________                                        ADSORPTION OF HERPES SIMPLEX VIRUS                                            TYPE W1-38 (10.sup.4.8 /ml CONCENTRATION)                                     Unadsorbed Viruses (as TCID.sub.50)                                           Type of Attapulgite Clay                                                                        Fine Grade Coarse Grade                                     ______________________________________                                        High Volatile Matter                                                                            <10.sup.0.0 /ml                                                                          <10.sup.0.0 /ml                                  Regular Volatile Matter                                                                         <10.sup.0.0 /ml                                                                          <10.sup.0.0 /ml                                  Low Volatile Matter                                                                             <10.sup.0.0 /ml                                                                          <10.sup.0.0 /ml                                  Sand (Control)      10.sup.4.8 /ml                                                                         --                                               ______________________________________                                    

Example 1 shows the adsorption of Herpes simplex virus designated astype Wl-38, supplied by the Wisconsin Alumni Research Foundation, as atypical virus having a relatively large molecular size of 0.2μ. Both DNAand RNA core organisms were used throughout the range of clay materialsevaluated for adsorption. In order to determine the adsorptivity of twodifferent grades of clay and for the three types of volatile mattercontent, the virus was made to contact the various types of clay in awet suspension. After contacting the various type clays for 2 minutes,the liquid containing the virus was then filtered and a determinationwas made on the amount of virus remaining in the liquid.

The method used in determining the concentration of virus remaining inthe liquid after contacting the clay is the indirect method of measuringthe effect of damage on live human tissue. The virus was prepared bymelting vials of frozen Herpes simplex virus materials and centrifuging1500 grams of the material for 10 minutes to remove any tissue debris.12 ml of virus material were added to a bottle containing 120 ml ofsterile distilled water.

The virus adsorption studies were carried out using the following testprocedure: 6 ml of virus culture material was added to a sterile bottlecontaining 60 ml of sterile distilled water. Aliquots (18 ml) of thediluted viral suspension were placed in a sterile 50 ml plasticcentrifuge tube containing 2 g of sterile adsorbent. The inoculated tubewas thoroughly mixed by shaking for 1 minute and immediately filteredthrough a sterile plastic filter unit containing a 0.45 micron Nalgenemembrane. The filtrates were titrated for virus infectivity in HEp IIcell system using a microscopic examination to determine cytopathiceffects. Virus counts are given as TCID₅₀ (tissue culture infectiousdose with a 50% response). The titration (or specific dilution sequence)technique used is described in "Methods for the Examination of PoultryBiologics," Chapter 2, National Research Council Publication 1038,National Academy of Science (1971) and in many standard textbooks onvirology. Clay concentrations were varied where desired. Ground sand wasrun as a control so that virus adsorption is reflected by the differencein titratable activity between any particular clay and the control.

For the various grades of clay utilized the test shown in Example 1, theadsorption properties for the high, regular and low volatile matter forthe Herpes simplex virus tested was equivalent for both the fine and thecoarse grades of clay. The TCID remaining in solution for the sandcontrol was 10⁴.8 /ml, which is equal to the concentration of virus inthe liquid solution before contacting. This shows that the variousgrades of attapulgite clay are, therefore, effective in removing all theHerpes simplex virus from solution whereas sand is completelyineffective.

                                      EXAMPLE 2.                                  __________________________________________________________________________    ADSORPTION OF POLIO VIRUS TYPE I (10.sup.7.2 /ml CONCENTRATION)               Unadsorbed Viruses (as TCID.sub.50)                                                              30           5                                                                Minutes Contact Time                                                                       Minutes Contact Time                          Type of Adsorbent  Fine Grade                                                                          Coarse Grade                                                                         Fine Grade                                                                          Coarse Grade                            __________________________________________________________________________    High Volatile Matter Attapulgite                                                                 <10.sup.0.0 /ml                                                                     <10.sup.0.0 /ml                                                                      10.sup.0.3 /ml                                                                      10.sup.0.3 /ml                          Regular Volatile Matter Attapulgite                                                              10.sup.1.0 /ml                                                                      10.sup.1.7 /ml                                                                       10.sup.0.7 /ml                                                                      10.sup.1.7 /ml                          Low Volatile Matter Attapulgite                                                                  10.sup.1.4 /ml                                                                      10.sup.2.5 /ml                                                                       10.sup.1.3 /ml                                                                      10.sup.2.0 /ml                          Sand (Control)     10.sup.7.2 /ml                                                                      --     10.sup.6.3 /ml                                                                      --                                      High Volatile Matter Sepiolite                                                                   <10.sup.0.0 /ml                                                                     --     --    --                                      Zeolex 80 (an amorphous                                                                          10.sup.1.0 /ml                                                                      --     --    --                                      zeolite)                                                                      __________________________________________________________________________

Example 2 shows the adsorption of polio type virus for various claymaterials. The effect of contact time is also shown for contacting thevirus-containing liquid with clay for 5 minutes and for 30 minutes. Thepolio virus type tested was Type I supplied by the Wisconsin AlumniResearch Foundation. This virus was used as exemplary of a smallmolecular size virus having a 0.2μ molecular size. The virus solutionswere prepared in a similar manner as for the Herpes simplex virusdescribed above and the TCID determination using human tissue is thesame as described earlier. The polio virus concentration for this testwas 10⁷.2 /ml. Example 2 shows that the attapulgite and sepiolite claysare effective for removing most of the polio virus from the liquidsolution after a contact period of 30 minutes. For a contact period of30 minutes the high volatile matter attapulgite clay showed 100%adsorption for both the fine and coarse grades compared to nearly 100%adsorption for both fine and coarse grades for a 5 minute contactperiod. Example 2, therefore, shows that the high volatile matterattapulgite clay is effective for removing substantially all traces ofpolio virus from a concentrated solution in a relatively short period ofcontact time. Zeolex 80, an amorphous or non-crystalline zeolite, whichis an example of a zeolite, was found to be equivalent to the regularvolatile matter attapulgite for polio virus adsorption for the sameincrement of contact time.

                                      EXAMPLE 3.                                  __________________________________________________________________________    ADSORPTION OF POLIO VIRUS TYPE I (10.sup.6.6 /ml CONCENTRATION)                                     Unadsorbed Viruses (as TCID.sub.50)                                    % Absorbent                                                                          Regular Volatile Matter                                                                    Low Volatile Matter                                                                      High Volatile                   __________________________________________________________________________                                                  Matter                          Fine Grade Attapulgite Clay                                                                  1.25   10.sup.6.8 /ml                                                                             --         --                              Fine Grade Attapulgite Clay                                                                  2.50   10.sup.3.6 /ml                                                                             --         --                              Fine Grade Attapulgite Clay                                                                  5.00   10.sup.3.3 /ml                                                                             10.sup.2.6 /ml                                                                             10.sup.1.2 /ml                Fine Grade Attapulgite Clay                                                                  10.00  10.sup.1.8 /ml                                                                             10.sup.2.3 /ml                                                                           <10.sup.0.0 /ml                 Fine Grade Attapulgite Clay                                                                  20.00  10.sup.1.3 /ml                                                                             10.sup.0.2 /ml                                                                           <10.sup.0.0 /ml                 Sand Control   10.00  10.sup.7.6 /ml                                                                             --         --                              __________________________________________________________________________

In order to determine the effect of the quantity of clay on theadsorption of polio virus the amount of clay was varied from 1.25% to20% for a fixed concentration of virus in solution. Examples 1 and 2indicate the adsorption based on a clay concentration of 10% by weightclay per weight of virus-containing liquid. Example 3 shows that for a10⁶.6 /ml polio virus concentration, 10% fine grade attapulgite clay insuspension is sufficient for removing substantial quantities of poliovirus from the liquid. Although attapulgite clay containing the threeclasses of volatile matter listed is effective for removing polio virusin different degrees depending upon the concentration of the variousclays in suspension, the high volatile matter is the most efficientadsorber for polio virus at all concentrations tested.

The examples shown above are indicative of the capability of the varioustypes of colloidal grade clay for effectively removing both relativelylarge particle diameter Herpes simplex type viruses and relatively smallparticle diameter polio type viruses from water. The phenomena thatcause adsorption are not well understood at this time but are postulatedto be related to such surfaces characteristics as the surface structureand available surface of the clay along with the effective positivecharge that these viruses assume, and the negative charge that the claysassume in a water solution. The volatile content as expressed by thedesignation of low, regular and high volatile matter is also indicativeas to the degree of disintegration that the various clays encounter uponcontact with water, and the amount of surface available after thesintering effect of heating. The disintegration process is brieflydescribed as the disassociation of the individual clay particles intoaccicular type needles having a 0.01μ diameter and a length of 1μ. Thecombination of the electrical attraction of the clay for cationicsubstances, such as viruses, and the ultrafine geometry of the clayneedles in suspension partially accounts for the very effectiveadsorption properties of the clay substances involved. The high volatilematter attapulgite clay readily disintegrates, as described above,whereas the regular volatile and low volatile matter disintegrate tolesser degrees, respectively.

The use of fine clay powders for removing polio and Herpes type virusesis suitable for both municipal and home type water supplies. This isparticularly important when such water supplies become accidentallycontaminated by negligent disposal of virus-contaminated substances orintentionally as in the event of germ warfare. The virus adsorbed uponthe clay surface in all the examples listed was found to remain viableand it was also discovered that the adsorption process is irreversible.If, for example, the clay is used to adsorb virus from potable watersupplies, the clay containing the virus should be removed so that theadsorbed virus could be destroyed by heat or chemicals.

The use of attapulgite clay powder in home swimming pools and aquariumsfor virus removal is also suggested in view of the good adsorptiveproperties of these clays for large and small virus molecules. In theseapplications the clay could be made to contact the virus by broadcastingin powder form over the surface of the swimming pool or aquarium, andremoved by standard sedimentation and/or filtration techniques. The useof clay for cleaning virus from swimming pools by adsorption is animportant application since the various infections and diseasestransmitted by persons using these pools are known to be of viralorigin.

The effect of clay powder as a means of adsorption of hormones fromwater is shown in Example 4. Although most hormones are insoluble inwater, diethylstilbesterol was chosen as an intermediate size moleculeto determine whether the good adsorption properties exhibited forviruses is also true for hormones. In this example two differentconcentrations of diethylstilbesterol (5 ppb and 50 ppb) were suspendedin water and were allowed to contact two different concentrations ofhigh volatile matter fine grade attapulgite clay. The amount of hormonesremaining in suspension was determined by known hormone analyticaltechniques. For the 1.1% clay concentration the amount of DES adsorbedwas 68% for 5 ppb compared to 60% for 50 ppb. 10% clay by weight ofwater containing 5 ppb DES adsorbed 76%, and adsorbed as much as 89% ofthe 50 ppb DES suspension. Example 4, therefore, shows that relativelysmall concentrations of clay are capable of removing substantialquantities of hormones from liquid suspensions.

                  EXAMPLE 4.                                                      ______________________________________                                        ADSORPTION OF DIETHYLSTILBESTEROL HORMONE                                     Attapulgite Clay   Percent DES Adsorbed                                       High Volatile Matter Fine Grade                                                                  5 ppb DES  50 ppb DES                                      ______________________________________                                         1.1%              68%        68%                                             10.0%              76%        89%                                             ______________________________________                                    

Example 5 shows the effective adsorption of a phosphate insecticide byhigh volatile matter attapulgite clay. Equal volumes of distilled waterwere contaminated with 100 ppb diazinon insecticide. Diazinon was chosenas an example of one of the pesticides available in different parts ofthe world. 10% attapulgite clay high volatile matter was added in powderform to a volume of distilled water contaminated with 100 ppb diazinon.The clay suspension was then shaken lightly to promote good contactbetween the clay surface and the liquid and subsequently poured througha fine grade micropore filter. The filtrate was then measured forconcentration of diazinon remaining in the solution by standardinsecticide determination analysis. The amount of diazinon remaining inthe filtrate after contact with the clay was 15%. An equal volume ofsand was added to an equivalent volume of diazinon-contaminateddistilled water and subjected to the same filtration and analysis as forthe clay. The amount of diazinon remaining in the filtrate from theliquid in contact with the sand was 57.5%. This shows that attapulgiteclay is very effective for removing traces of this insecticide fromwater and may find possible aplication as an internally administeredantidote for treatment of insecticide poisoning as well as for removinginsecticides from potable water supplies.

                  EXAMPLE 5.                                                      ______________________________________                                        ADSORPTION                                                                    OF DIAZINON INSECTICIDE (100 ppb DOSAGE)                                                      Percent                                                       10% Adsorbent   Diazinon Remaining In Solution                                ______________________________________                                        High Volatile Matter                                                                          15.0%                                                         Fine Grade                                                                    Sand Control    57.5%                                                         ______________________________________                                    

In order to determine the effect of clay for removing cadmium ions fromcontaminated water supplies, the following tests were performed.

1% and 10% concentrations of fine ground HVM attapulgite clay were addedto water contaminated with cadmium. Since the adsorption of various ionsis known to be dependent upon the pH of the liquid medium, theadsorption studies were made at both a pH value of 6 and a pH value of10. Samples were prepared using distilled water to which 1 ppmconcentration of salts were added. After contacting the contaminatedwater with the various concentrations of clay and the 10% sand control,the contaminated liquids were filtered and the filtrates were analyzedfor cadmium ion content by standard methods of quantitative analysis.For all the samples tested it was found that both the 1% and 10% clayconcentrations were very effective for removing cadmium ions fromsolution. Examples 6 indicates the possible use of attapulgite clay asan antidote for the ingestion of poisonous cadmium salts as well as forremoving the ion from the contaminated water supplies.

                  EXAMPLE 6.                                                      ______________________________________                                        ADSORPTION OF CADMIUM IONS                                                    (1 ppm CONCENTRATION)                                                                            ppm Remaining                                                                 In Solution                                                Fine Attapulgite Clay                                                                              Cadmium                                                  High Volatile Matter pH 6.0   10.0                                            ______________________________________                                         1%                  0.04     0.14                                            10%                  < 0.03   0.04                                            Sand Controls        0.78     0.72                                            ______________________________________                                    

In order to determine the effect of clay on removing mycotoxins fromwater, the following tests were performed and the results are shown inExamples 7.

                  EXAMPLE 7                                                       ______________________________________                                        ADSORPTION OF AFLAVOTOXINS                                                                 % Aflavotoxin Adsorbed                                           High Volatile Matter                                                                         0.5 ppb       5.0 ppb                                          Fine Attapulqite Clay                                                                        Concentration Concentration                                    ______________________________________                                         1.0%          100.0%        >97.5%                                           10.0%          100.0%        100.0%                                           ______________________________________                                    

Since find grade high volatile matter attapulgite clay has been shown tobe an effective contact adsorbent for all materials tested, thismaterial was used at 1.0% and 10% concentrations in order to removemycotoxins from water. Aflavotoxins were selected as characteristic of alarge group of mycotoxins which could be found in contaminated watersupplies particularly if drainage from mold infested agriculturalproducts enters the water supplies. The aflavotoxins were added todistilled water in concentrations of 0.5 ppb and 5 ppb, respectively.For the 1.0% concentration of clay added to the 0.5 ppb concentration itwas found that 100% of the aflavotoxins were adsorbed and for the 5 ppbconcentration greater than 97% were adsorbed. For the 10% clay added toboth the 0.5 ppb contaminated water and the 5.0 ppb contaminated water,the amount of aflavotoxins adsorbed was 100%. The mycotoxin content wasdetermined by standard methods of analysis. Example 7 indicates,therefore, that fine grade high volatile matter attapulgite clay is veryeffective for removing mycotoxin contaminants from water using contactadsorption.

The efficient decontamination of potable water by contact adsorption hasbeen shown by the use of various grade clays and suggests applicationfor ecological improvement of inland surface and well waters byrelatively inexpensive clay treatment. The use of fine grade highvolatile matter attapulgite is effective for removing impurities fromwater supplies, swimming pools, aquariums, and for the treatment of homeand municipal fluid waste materials. The method suggests contacting theclay material with the contaminated water by either broadcasting aneffective quantity of powder over the surface of the water or by passingthe contaminated water through a bed containing the clay particlesdeposited upon an inert filter substance.

While the contacting technique for water purification is feasible inmany existing sewage treatment and municipal water supply treatmentplants, there are many possible situations where percolation treatmentwould be more desirable and/or advantageous. Percolation is defined forthe purpose of this invention as the passing of the contaminated waterthrough a column packed with granular adsorbent. Columns are generallyvertical and directional flow either with or against the force ofgravity can be employed.

When this method is practiced only the granular LVM (calcined) grades ofclay can be utilized. The LVM grades are necessary because they are theonly ones that will maintain their shape without disintegrating inwater; granular grades are specified because inter-granular passagesmust exist to allow a free path for the water to pass through thecolumn. Amounts of adsorption occurring or capacity in percolation aregenerally anticipated to show some sort of inverse relationship to thethroughput rate and the size of the material being adsorbed -- e.g. (1)high percolation rates will show lower column capacities than lowpercolation rates and (2) larger particle size water contaminants suchas viruses will show much lower adsorbency than molecular-sized or ioniccontaminants because of the differences in surface available to each.

To demonstrate the utilization of this invention for contaminant removalusing the percolation technique, runs were tried with water containingdiazinon, aflatoxin B₁ and diethylstilbesterol. The percolation columnused consisted of a Chromoflex column, K4203020, size 256 (int. diam.1.7 inches) with a sintered glass disk at its base plus a teflonneedle-valve to control flow. A 30/60 mesh attapulgite granular LVM claywas used to pack the column. A 300 g portion filled the column to aheight of ˜15 inches. Prior to these runs Methylene blue chlorideexperiments were carried out at the proposed throughput rates todetermined that these column dimensions were adequate to prevent bypassand channeling.

As a first step in the evaluations to determine column capacities forcontaminants, the columns were flushed with sterile water to wash outfines. Contaminated water was run in on top of the column before thefinal water was drained and this retained volume was subtracted from thefinal percolation volume. Rates used were 20 and 60 cc/minute(equivalent to 960 gallons/ton/hour and 2882 gallons/ton/hour). Effluentmaterials were checked without filtration using standard analyticaltechniques. Water samples evaluated for percolation adsorption werecontaminated with: (1) 20 ppb of aflatoxin B₁ as an example of amycotoxin and shown in Example 8; (2) 100 ppm diazinon as an example ofa phosphate pesticide and shown in Example 9; and (3) 50 ppb ofdiethylstilbesterol as an example of a hormone and shown in Example 10.

                  EXAMPLE 8                                                       ______________________________________                                        PERCOLATION SORPTION OF 20 ppb                                                AFLATOXIN B.sub.1 SOLUTION BY 30/60 LVM ATTAPULGITE                                              Filtrate Evaluation                                        Percolation Time   for Aflatoxin B.sub.1                                      ______________________________________                                                           20 cc/minute flow rate                                     1 hour              not detectable                                            2 hours             not detectable                                            4.25 hours          not detectable                                                               60 cc/minute flow rate                                     20 minutes          not detectable                                            40 minutes          not detectable                                            100 minutes         not detectable                                            ______________________________________                                    

                  EXAMPLE 9.                                                      ______________________________________                                        PERCOLATION SORPTION OF 100 ppb DIAZINON                                      SOLUTION BY 30/60 LVM ATTAPULGITE                                                                Filtrate Evaluation                                        Percolation Time   for Diazinon                                               ______________________________________                                                           20 cc/minute flow rate                                     1 hour              not detectable                                            2 hours             not detectable                                            4.25 hours          45 ppb                                                                       60 cc/minute flow rate                                     20 minutes          not detectable                                            40 minutes          10 ppb                                                    100 minutes         65 ppb                                                    ______________________________________                                    

                  EXAMPLE 10.                                                     ______________________________________                                        PERCOLATION SORPTION OF 50 ppb                                                DIETHYLSTILBESTEROL SOLUTION BY 30/60 LVM ATTAPULGITE                                            Filtrate Evaluation                                        Percolation Time   for DES                                                    ______________________________________                                                           20 cc/minute flow rate                                     1 hour             0 ppb                                                      2 hours            0 ppb                                                      4.25 hours         0 ppb                                                                         60 cc/minute flow rate                                     20 minutes         0 ppb                                                      40 minutes         1 ppb                                                      100 minutes        2 ppb                                                      ______________________________________                                    

Translating these results into gallons per ton capacity of the clay forcontaminants, they are summarized in Example 11.

                  EXAMPLE 11.                                                     ______________________________________                                        CAPACITIES OF 30/60 LVM ATTAPULGITE FOR WATER CONTAMINANTS                                Percolation           Column                                                  Rate          Time    Capacity                                    Contaminant (gals./ton/hr.)                                                                             (hrs.)  (gals./ton)                                 ______________________________________                                        20 ppb Aflatoxin                                                                           960          4.25    >4100                                                   2882          1.67    >4800                                       100 ppb Diazinon                                                                           960          2.0     Between                                                 2882          0.33    1920 & 4100                                                                   Between                                                                       961 & 1921                                  50 ppb       960          4.25    >4100                                       Diethylstil-                                                                              2882          0.33    Between                                     besterol                          960 & 1921                                  ______________________________________                                    

Another example of the use of the percolation technique to improve thepotability of contaminated water is shown in Example 12 for watersolutions of the heavy metal cations arsenic, cadmium, lead and mercury.Each cation was dissolved in an acid solution at about 1.00 ppm. Thepercolation column was as described above using 30/60 LVM attapulgite.Throughput rates were 20 cc/minute and 60 cc/minute. Column effluentswere not filtered but were examined for each contaminating ion bystandard methods of quantitative analysis.

                  EXAMPLE 12.                                                     ______________________________________                                        PERCOLATION ADSORPTION OF HEAVY METAL CATIONS                                 Percolation Rate                                                                         Effluent Concentrations in ppm                                     at Times Shown                                                                           Arsenic   Cadmium   Lead   Mercury                                 ______________________________________                                        20 cc/min.                                                                    1 hr.      0.02      <0.01     <0.01  0.004                                   2 hrs.     0.12      <0.01     <0.01  0.016                                   4.5 hrs.   0.56      <0.01     <0.01  0.116                                   Original Conc.                                                                           0.97       1.00      1.07  1.11                                    60 cc/min.                                                                    20 min.    0.33      <0.01     <0.01  0.010                                   40 min.    0.16      <0.01     <0.01  0.072                                   100 min.   0.68      <0.01     <0.01  0.152                                   Original Conc.                                                                           1.02       1.00      1.07  1.11                                    ______________________________________                                    

These data illustrate the efficient sorptivity of the granular LVMattapulgite for cadmium, lead and mercury and the fairly good capacityof the clay for arsenic.

As previously indicated, the column efficiency was better at the lowerrate. This is obvious when the sorptivity for mercury and arsenic iscompared at equal throughput volumes (20 cc/min. at 2 hours and 60cc/minute at 40 minutes).

Outside of standard methods of treating municipal and industrial watersupplies such as broadcasting the clay powder along with alum followedby sedimentation and filtration the rapid adsorptive properties for theclay samples tested suggested the following home-type applications.

FIG. 1 shows a metal or plastic container 2 having an inlet 4 and outlet6. A fine grade filter 8 can also be inserted within the container 2 toprevent materials from passing through the outlet 6. Particulate claymaterial 10 is enclosed within the container 2 between the inlet 4 andoutlet 6. Incoming water through inlet 4 would then transport bypercolating through the clay material 10 where adsorption would occur.The treated water would then pass out the outlet 6. The granular claymaterial 10 could be periodically removed and replaced in order toprovide continuously active surfaces for adsorption. If desired otheradsorbing materials such as charcoal and sand could be used incombination with the clay material.

FIG. 2 shows another embodiment for providing contact between thegranular clay adsorbent and the water to be treated. A coiled tubing 1having an inlet 3 at one end and an outlet 5 at another end contains acoating of clay material on the inner surface of the tubing. Byadjusting the tubing diameter, the number of coil turns and the waterflow rate, the water could be made to effectively wet the clay forefficient contact and adsorption.

FIG. 3 shows a cross-section of the tube 1 having a tube wall 7containing a coating of particulate clay material 9. The tubing 1 couldbe replaced after the clay material 9 is no longer capable ofadsorption, or the clay material 9 could be dissolved, removed andreplaced. The tubing 1 made from commercially available metal or plasticmaterial could also be made from the clay itself. In this applicationthe outer surface of the tubing would have to be glazed or treated toinsure that the pipe is non-porous.

Although the invention is directed to methods and materials for removingsubstances such as hormones, pesticides, viruses, toxins and metal saltsfrom water supplies for home, industrial and municipal applications,this is by no means intended as a limitation thereof. The use of clayreadily finds application, for example, in military and other mobiletype circumstances where the only source of water is known to becontaminated to where methods of prevention of contamination of drinkingsources may be required. The method also finds application in thetreatment of sewage effluents from municipal treatment plants to preventsurface water contamination as well as in finishing processes forindustrial wastes.

What is claimed is:
 1. A method for purifying water comprising the stepsof:contacting the water with large surface area clay particles selectedfrom the group of natural clays consisting of attapulgite and sepiolite;adsorbing toxins on the clay surface; and separating the water from saidclay containing said toxins.
 2. The method of claim 1 wherein said claycomprises a colloidal grade clay.
 3. The method of claim 1 wherein saidsurface area is at least 50 square meters/gram available surface.
 4. Themethod of claim 1 including the step of treating the water with alum. 5.The method of claim 1 including the step of contacting said water withcharcoal.
 6. The method of claim 1 wherein said step of contacting saidwater with said large surface area clay particles comprises broadcastingsaid particles in powdered form over the surface of said water.
 7. Themethod of claim 1 wherein said step of contacting said water with saidlarge surface area clay particles comprises passing said water through apipe containing said clay particles.
 8. The method of claim 7 whereinsaid clay particles are coated on an inner surface of said pipe.
 9. Themethod of claim 7 wherein the surface of said pipe is at least partiallycomposed of the adsorbing clay.
 10. The method of claim 1 wherein saidstep of contacting comprises percolating the water through said clayparticles in granular form.
 11. A method for purifying contaminatedwater containing toxins comprising the steps of:treating said water byadding a flocculating chemical to coagulate and settle at least part ofsaid toxins from said water; filtering said treated water to remove afurther part of said toxins; treating said filtered water with achemical germicide to kill bacteria; and contacting saidgermicide-treated water with large surface area clay particles selectedfrom the group of natural clays consisting of attapulgite and sepioliteto remove remaining toxins from the water.
 12. The method of claim 11wherein said clay comprises colloidal grade clays.
 13. The method ofclaim 11 wherein said flocculating chemical is selected from the groupconsisting of alum and ferric sulfate.
 14. A method of purifying waterfor human consumption comprising the steps of:contacting the water witha flocculating chemical and large surface area clay particles selectedfrom the group of natural clays consisting of attapulgite and sepioliteto adsorb toxins from said water; settling said toxin-containingflocculating chemical and large surface area clay particles to remove atleast part of said toxins from said water; filtering said water toremove a further part of said toxins; and chemically treating saidfiltered water to render said water safe for human consumption.